INTEGRATED MAGNETIC-FIELD SENSOR

For small magnetic field measurements, Sextant Avionique is developing, in collaboration with the Ecole Superieure d'Ingenieurs en Electrotechnique et Electronique, a new generation of miniature sensors. The detector is a mechanical resonator using a monocrystalline silicon beam. The excitation of this resonator is achieved through the Laplace force, operating on an alternating current flowing through a conductor deposited on the beam. The oscillation amplitude, which is proportional to the external magnetic field, is detected through a piezoresistive gauge bridge diffused in the silicon beam. The mechanical properties of the silicon and the resulting quality factor of the resonator have allowed a very sensitive device to be designed with a resolution in the nanotesla range. The manufacture of the resonator is possible through extensive use of micromachining and microelectronic technologies. It is then possible to produce a single wafer incorporating hundreds of small transducers at a very low unit cost.